Heat sources in electronic devices and the like are generally cooled by causing a fan to rotate. A method for controlling fan rotation includes a technique of detecting the current consumption of boards provided in a device housing and then controlling a fan rotation speed to generate an amount of airflow corresponding to the number of boards based on the detection result. Further, a fan rotation control technique is provided that controls the noise generated by the fan rotation while executing, for example, a special application such as listening to music and the like.
Temperature variations as illustrated in FIG. 1 may occur when controlling fan rotation based on the temperature of a heat source detected by a temperature sensor. FIG. 1 is a graph with time described on the horizontal axis and temperature described on the vertical axis. When the fan rotation is increased as the temperature of the heat source reaches and exceeds a threshold (T1), no immediate cooling effect is seen as illustrated in FIG. 1. The temperature continues to rise for a short time to exceed a fixed temperature (T2). When the temperature exceeds the fixed temperature (T2) as illustrated in FIG. 1, a function to lower the frequency of an IC (integral circuit) to avoid breakdown is implemented if the heat source is a processor.
When the temperature of the processor rises excessively and the function to lower the IC frequency is implemented in this way, the performance of the processor decreases.